There is a fundamental gap in understanding the effects of normal and abnormal calcium signals on their protein targets. The long-term goal of this research is to develop chemical tools that may be used to elucidate the molecular-level structural and functional consequences of normal and abnormal calcium signals. The overall objective of this grant application is the development of a novel method to mimic a wide range of physiological calcium signaling patterns in vitro with potential for use in vivo. The central hypothesis of this application is that organic compounds known to undergo reversible structural changes in response to light (photochromic compounds) may be modified with appropriate ligands to create a reversible cage for calcium. The rationale for the proposed research is that, once developed, this method will be used to decipher the effects of calcium signals, eventually leading to insights about both normal and unhealthy conditions in humans. Thus, the proposed research is relevant to NIH's mission. We plan to test our central hypothesis and accomplish the objective of this application by pursuing the following two Specific Aims. 1). Increase the metal binding affinity and Ca2+ selectivity of the naphthopyran-based chelator for mimicking calcium signals under physiological conditions. 2) Tune the binding properties of the reversible photoswitch to achieve larger amplitude oscillatory calcium signals. This project is innovative because it will create methodology that may be used to investigate the effects of dynamic calcium signaling without initiating an entire signal transduction cascade. The proposed research is significant, because it is expected to contribute a chemical tool that may be used to advance understanding of calcium signaling as well as to elucidate the molecular basis of certain diseases associated with calcium signaling.